1. Field of the Invention
The present invention relates to crimping jaws of the type used to assemble compression sleeves onto lengths of pipe to form compression couplings, sometimes referred to as compression joints. In particular, the invention relates to energy efficient dies for such jaws for crimping such fittings in an improved manner.
2. Description of the Related Art
A compression coupling comprises a generally tubular compression sleeve (sometimes referred to as a compression fitting) containing an O-ring which is compressed in radial directions in order to engage the compression sleeves with the respective ends of pipes, and in so doing, form a leak resistant joint between the pipe ends. The joint itself has considerable mechanical strength and is self supporting in the absence of ancillary support members.
In the present application “crimping jaw” refers to the actual device which includes crimping dies for forming a compression joint. For example, a common form of crimping jaw is disclosed in commonly assigned U.S. Pat. No. 5,611,236 to Grunwald, which includes a pliers-type device having crimping dies attached thereto for crimping compression sleeves. This pliers-type device is generally operated with a power tool which spreads the free ends of the plier arms to squeeze the jaws about the sleeve/pipe combination to form a compression joint. Other devices known to persons skilled in the art such as “non-plier” type jaws are also contemplated for use with the present dies.
In order to form a successful compression joint with a crimping jaw using a compression sleeve, one of the major considerations is that the crimping jaw shall not scuff, cut, scrape or gouge the compression sleeve during the crimping operation.
Further, as noted in the Grunwald '236 patent, it is essential that the crimping dies of the jaw approach each other in end-to-end parallelism. If the dies do not engage each other in end-to-end parallelism, then, there is a probability of pinching and cutting of the compression sleeve at certain points around the circumference thereof, while other points on the circumference of the compression sleeve are not fully compressed. In known jaws such pinching and “bunching-up” of compression sleeve material has been known to occur at the interfaces of the dies. This condition can result in a faulty joint, in that a blow-out and leakage can occur at the damaged portion of the compression sleeve when the pipe line is subjected to pressure, and, in the alternative, leakage axially of the pipe can occur at the insufficiently compressed portions of the compression sleeve.
Crimping jaws used for assembling compression sleeves with pipes or tubes are required to include crimping dies that can move radially and somewhat circumferentially with respect to the central longitudinal axis of the compression sleeve. A simple pliers-type crimping jaw cannot successfully accomplish precisely the desired movements because the dies of the pliers each move on an arcuate path. In such instance, the result is that considerably more force is exerted on the compression sleeve on its radius closest to the pivot axis of the pliers, causing the sleeve to shift within the jaw, with the potential danger of cutting the compression sleeve. At the same time the compressive force which is exerted at the diametrically opposite radius would be lesser and insufficient. Furthermore, substantial losses of crimping energy are encountered due to the friction forces developed between the dies and the sleeve, and particularly at each interface between the dies wherein the outer surface material of the sleeve tends to “bunch-up” and form raised portions on the periphery of the sleeve.
I have invented a crimping die for such compression jaws which significantly reduces the friction developed between the dies and the compression sleeve by the provision of unique rollers on the dies, which produce limited, but sufficient crimps on the sleeve/pipe combination, while providing a much improved sleeve/pipe attachment and utilizing less-crimping energy, and force. In particular, the present invention applies less force to produce an improved attachment with less utilization of energy.